The present invention relates to control panel assemblies and a method of making components such as buttons and bezels for use in control panels. More particularly, the present invention is directed to backlit control panel assemblies having indicia that is visible during daytime and nighttime usage.
Control panels having backlit buttons are known for use in the interior of automotive vehicles, including radio control buttons and door lock buttons. The purpose of backlit buttons is to allow a user to see the button and its function even in low light situations. Typically, a radio button will have a graphic image or other indicia to indicate a particular purpose. For example, the word xe2x80x9cscanxe2x80x9d or a number such as xe2x80x9c3xe2x80x9d is provided on a button to indicate that button""s purpose. One known button is made by injection molding a clear plastic material in the form of a button. The button is then painted with a layer of white paint and dried by an oven or other conventional technique. Next, a layer of black paint is applied over the white paint and is subsequently dried. A laser is used to etch away a desired portion of the black paint to form a white graphic image. In a low light situation, the button is illuminated from behind such that the graphic image is visible to a user through the white paint layer.
Another known method of making buttons for a control panel involves providing a transparent member with a black layer on one side and vacuum forming the transparent member with the black layer into a desired shape. Thereafter, a laser passes through the transparent member and etches away a desired portion of the black layer to form a graphic image. Next, a daytime color is pad printed over the black layer side and dried in an oven followed by pad printing a nighttime color on top of the daytime color and oven drying the nighttime color. Finally, the subassembly is placed in an injection molding apparatus and an interior recess of the button is filled with resin during injection molding to make the button more rigid.
It is further known to provide control panels having backlit buttons on a switch pad for resilient switching action. However, the known buttons have a generally flat upper surface to be sure that light can fully reach and evenly illuminate a graphic image on the button. In addition, the graphic image may be partially blocked from illuminating light by part of the switch mat because of the way the button rests on the switch mat. Thus, the graphic image will not be fully visible when backlit.
The present invention is directed to a control panel assembly and to individual components of that assembly, including, a bezel containing at least one opening and at least one button associated with the bezel. The bezel and/or the button have a main body vacuum formed into a predetermined shape and having an inner surface and an outer surface. The main body includes coextruded first and second layers and a third layer applied to the second layer. Further, the first layer is generally transparent, the second layer is generally translucent, and the third layer is generally opaque. In addition, a resilient switch mat is associated with the at least one button and comprises a generally planar base portion with at least one generally hollow projection for contacting the button. The projection has first and second ends and inner and outer surfaces. Further, the first end of the projection includes a stepped portion for receiving a portion of the button.
Additionally, the present invention can include indicia on the outer surface of the main body of the bezel and/or button. Preferably, the indicia is laser etched into the opaque layer thereby exposing the translucent layer. The transparent first layer can have a thickness of approximately 0.040 inch. Next, the translucent second layer is a color layer and can have a thickness of approximately 0.008 inch. The opaque third layer can have a thickness of approximately 0.002 inch. Moreover, the opaque third layer is thermally bonded to the coextruded first and second layers, according to one version of the present invention. In a preferred embodiment of the present invention, the transparent first layer is an interior layer, the translucent second layer is a middle layer, and the opaque third layer is an exterior layer.
The switch mat of the present invention further includes the stepped portion having a shoulder located a predetermined distance away from the first end of the projection for limiting travel of a button relative to the projection. And, the second end of the projection is connected to the generally planar sheet. In addition, the inner surface of the projection has variable thickness that is created by at least one axial groove provided on the projection for increasing interior cross-sectional area for light to pass to the at least one button for fully illuminating any indicia thereon. Further, the projection includes corners having a cross-sectional thickness greater than an adjacent side wall portion for insuring lateral strength of the projection. One disclosed version includes the projection having a generally rectangular cross-sectional shape.
The present invention is also directed to a method of making a component of a control panel comprising the steps of: providing a first layer of material, providing a second layer of material and coextruding the first layer of material to the second layer of material. The method also includes forming the coextruded first and second layers into a predetermined shape.
Another method step of the present invention involves applying a third layer of material onto the coextruded first and second layers. The step of applying can be carried out by at least one of thermally bonding, spraying, or printing. Still further, the forming step is optionally, but preferably performed after the step of applying the third layer to improve processing and quality. More specifically, the step of forming can include vacuum forming.
The coextruding step further includes the first layer of material being generally transparent and the second layer of material being generally translucent. The forming step can include vacuum forming either a bezel, a button or both. Also, the method of the present invention includes providing indicia on the component.
Yet another method according to the present invention includes forming a component for a control panel comprising the steps of: providing a first layer of material, providing a second layer of material, coextruding the first layer of material to the second layer of material, vacuum forming the coextruded first and second layers into a predetermined shape, applying a third layer of material to the second layer, and selectively removing a portion of the third layer of material to expose a portion of the second layer for forming indicia on the component.
The present invention provides a control panel assembly and components that are more cost effective to fabricate and eliminates extra steps that are required to make previously known components. Control panel components provided in accordance with the present invention have an inner transparent layer, a middle translucent color layer, and an opaque outer surface layer. Indicia can be provided on the button or bezel using a laser etching technique that removes a predetermined portion of the opaque outer surface layer. The component can be vacuum formed from a multi-layer sheet that includes a co-extruded substrate having a generally transparent layer co-extruded with one or more translucent color layers. A thin outer opaque layer is thermally bonded to the co-extruded substrate using residual heat remaining from the co-extrusion process. Next the multi-layer sheet is vacuum formed to create a any number of components. As a result, the steps of painting multiple coats and drying each coat has been eliminated. Thus, environmental concerns associated with painting are eliminated. Further, the present invention provides a more uniform thickness to the outer opaque layer than is provided by painting. Moreover, the inner transparent layer is made sufficiently thick to provide adequate strength for the button, thereby eliminating the need to injection mold resin behind the button as in the prior art. By eliminating the injection molding step, the present invention substantially reduces tooling costs and tooling time versus known button making processes. In addition, cycle time to process the button is reduced from approximately 30 seconds to approximately 6 seconds. Therefore, costs of fabricating buttons is substantially reduced in accordance with the present invention.
The control panel assembly of the present invention further includes an elastomeric switch mat having a planar sheet portion with a plurality of projections that correspond to locations of buttons. Each projection has first and second ends and are generally hollow having side walls with inner and outer surfaces. The switch mat covers a printed circuit board having a light source. A projection channels light from the light source up to the button mounted thereon and allows the button to be backlit. Preferably, a stepped portion is provided at the first end of the projection for receiving the button. A shoulder is provided to act as a stop which limits the travel of the button onto the projection and spaces the inner surface layer of the button away from the first end of the projection to enable the light source to fully illuminate any indicia located on the button. Moreover, the side walls of the projections have variable thickness and include axial grooves to allow light to reach the inner surface layer of the button. The present invention therefore allows buttons having greater arcuately shaped or contoured top surfaces to be used without the drawback of having idicia being blocked off from light by a side wall of the projection.
As a result, the present invention provides a control panel assembly such as those used on the interior of automotive vehicles that are cost effective, have improved feel to the user and have indicia that will not be rubbed off during its service life.